Replace issue-129 and zopfli tests

tests/flags.rs

@@ -686,9 +686,9 @@ fn zopfli_mode() {
         input,
         &output,
         &opts,
-        INDEXED,
+        RGB,
         BitDepth::Eight,
-        INDEXED,
+        RGB,
         BitDepth::Eight,
     );
 }

tests/reduction.rs

@@ -386,6 +386,18 @@ fn rgb_8_should_be_palette_8() {
     );
 }
 
+#[test]
+fn rgb_trns_8_should_be_palette_8() {
+    test_it_converts(
+        "tests/files/rgb_trns_8_should_be_palette_8.png",
+        false,
+        RGB,
+        BitDepth::Eight,
+        INDEXED,
+        BitDepth::Eight,
+    );
+}
+
 #[test]
 fn rgb_16_should_be_palette_4() {
     test_it_converts(

tests/regression.rs

@@ -7,7 +7,6 @@ use std::{
 use oxipng::{internal_tests::*, *};
 
 const GRAYSCALE: u8 = 0;
-const RGB: u8 = 2;
 const INDEXED: u8 = 3;
 const GRAYSCALE_ALPHA: u8 = 4;
 const RGBA: u8 = 6;
@@ -150,18 +149,6 @@ fn issue_89() {
     );
 }
 
-#[test]
-fn issue_129() {
-    test_it_converts(
-        "tests/files/issue-129.png",
-        None,
-        RGB,
-        BitDepth::Eight,
-        INDEXED,
-        BitDepth::Eight,
-    );
-}
-
 #[test]
 fn issue_140() {
     test_it_converts(